Role of cytosolic liver fatty acid binding protein in hepatocellular oxidative stress: effect of dexamethasone and clofibrate treatment

Abstract

The presence of cysteine and methionine groups together with an ability to bind long-chain fatty acid (LCFA) oxidation products makes liver fatty acid binding protein (L-FABP) an attractive candidate against hepatocellular oxidative stress. In this report, we show that pharmacological treatment directed at modulating L-FABP level affected hepatocellular oxidant status. L-FABP expressing 1548-hepatoma cells, treated with dexamethasone or clofibrate, decreased and increased intracellular L-FABP levels, respectively. Oxidative stress was induced by H2O2 incubation or hypoxia-reoxygenation. The fluorescent marker, dichlorofluorescein (DCF), was employed to measure intracellular reactive oxygen species (ROS). Hepatocellular damage was assessed by lactate dehydrogenase (LDH) level. Dexamethasone treatment resulted in a significant increase in DCF fluorescence with higher LDH release compared to control cells. Clofibrate treatment, however, resulted in a significant decrease in both parameters (p<0.05). Drug treatments did not affect cytosolic activities of glutathione peroxidase (GPx), superoxide dismutase (SOD), or catalase suggesting that the differences between treated and control cells may likely be associated with varying L-FABP levels. We conclude that L-FABP may act as an effective endogenous cytoprotectant against hepatocellular oxidative stress.

Molecular mechanism of recombinant liver fatty acid binding protein's antioxidant activity

“…Nonspecifi c antibody binding was blocked by preincubation of membranes in 1× TBS containing 5% skim milk for 1 h at room temperature. Membranes were then incubated overnight at 4°C with a polyclonal antibody raised against rat L-FABP as described previously ( 22 ) in 1× TBS containing 5% skim milk. After being washed, membranes were incubated with donkey anti-rabbit IgG (Amersham) at 1:500 dilution for 1 h (room temperature).…”

“…By binding polyunsaturated fatty acids, L-FABP modulates the availability of these fatty acids to intracellular oxidative pathways ( 19 ) and in this manner controls the amount of reactive oxygen species (ROS) released within the cell from this pathway. In addition to these well-known functions, recent studies have shown that L-FABP plays a further role in the cellular antioxidant defense mechanism (20)(21)(22). Using an L-FABP cDNA transfection model Wang et al ( 20 ) reported that hepatocytes containing L-FABP were associated with much lower levels of ROS compared with hepatocytes devoid of L-FABP.…”

“…Since intracellular L-FABP has been reported to play a major role in suppressing oxidative stress ( 20,22 ), a reduction in ROS by L-FABP would be observed in an in vitro DCF oxidation assay. As shown in Fig.…”

Procaterol but Not Dexamethasone Protects 16HBE Cells From H2O2-Induced Oxidative Stress

“…In a previous study, H 2 O 2 -induced oxidative stress also reduces the effect of dexamethasone on the IL-8 release in the airway epithelium (29). In terms of other cells, although dexamethasone reduces H 2 O 2 -induced macrophages apoptosis in a few studies (15), many more studies found that dexamethasone could not reduce H 2 O 2 -induced oxidative stress and apoptosis (16,25). Moreover, dexamethasone can directly induce oxidative stress in osteoblasts and hippocampal cells (30).…”

“…Moreover, due to the glucocorticoid resistance (GR) phenomenon, the clinical benefits of corticosteroid therapy in COPD are limited (14). At the cellular level, the pharmacological effects of dexamethasone appear to be controversial when it treats H 2 O 2 -induced oxidative stress (15,16). Thus, whether dexamethasone can relieve H 2 O 2 -induced oxidative stress in 16HBE cells is an interesting topic for further study.…”